Boring device for opening passages to branch portions of a lined main pipe line

ABSTRACT

A boring device for a lining material in a branched portion of a lined pipe such as a gas-conduit or a city water pipe line to which the lining material has been applied, which device includes a tension coil spring 1, a compression coil spring 2 being connected to the tip of the tension coil spring and having a spring constant smaller than that of the tension coil spring, a head element 5 in the form of a circular truncated cone being connected to the tip of the compression coil spring 2 and having an electric heat-generating device 3 coated with a thermoplastic resin and a single or plural transmission wires 9 being connected to the heat-generating device 3 and being passed in a loosened state through the tension coil spring 1 and the compression coil spring 2, the transmission wires 9 being fixed within the tension coil spring 1 at plural points, and a device N provided in rear of the tension coil spring for rotatably extending the device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a boring device for a lining materialhaving been applied onto the inner surface of a pipe line having abranched portion, which device can bore the lining material in thebranched portion to communicate the branched pipe line to the main pipeline, and more particularly, to a boring device which is inserted fromthe branched pipe line having a smaller diameter and to the branchedportion where the lining material is bored.

2. Description of the Prior Art

In general, a lining treatment for pipe lines, chiefly those buried inthe ground, such as gas conduits and city water pipe lines, is carriedout for the purpose of repairing or reinforcing the pipe lines.

As a method for lining, there is known a method which is carried out insuch a manner that a tubular lining material made of a flexiblematerial, which has been provided on the inner, leading surface thereofwith a binder, is annularly fixed at one end thereof and fluid pressureis applied to the back surface of the annularly fixed portion to form aturning point such that the lining material is turned inside out whichallows the turning point to advance within the pipe line therebyinserting the evaginated lining material into the pipe line, whilepressing the surface of the lining material, onto which the binder hasbeen applied, against the inner surface of the pipe line by the fluidpressure and solidifying the binder to effect bonding. This method has anumber of merits. It is unnecessary to dig up a pipe line over its fulllength and the method is operable simply by digging the pipe line onlyat both terminal ends thereof to be treated, and the lining work itselfcan be done within a very short period of time even for a long pipeline. In recent years, therefore, this method has attracted specialpublic attention.

In case a pipe line is lined according to this method wherein a tubularlining material is bonded to the entire inner surface of the pipe line,however, a passage with branch pipe lines off the main pipe line willhave their entrances blocked. In the case of a gas conduit, for example,such problem will not arise in a high or middle pressure pipe line as atrunk conduit, because the line is usually devoid of any branchedportion. In the case of a terminal low pressure pipe line, however,there are a number of branched supply pipe lines for supplying gasaccording to the unit of users, for example, the number of families.

Thus, the passages to the supply pipe lines will be blocked when the lowpressure pipe line is lined according to the above mentioned method. Insuch a case, digging up the branched portions from the ground for boringthe lining material after the lining treatment will make no substantialdifference from digging up the entire pipe line over its full length,thus losing the greatest merit of this lining method.

Accordingly, there is a demand for developing a simple and easy meansfor boring the applied lining material at the branched portions afterthe pipe-lining treatment to communicate the branched pipe lines to themain pipe line without digging up the branched portion from the ground.

A method is known wherein a cart movable by remote control and a devicefor detecting a branched portion to a branched pipe line, such as aTV-camera, movable together with the cart, are disposed within a linedpipe line, and a boring head installed on the cart is moved freely inboth circumferential and radial directions within the pipe line to thebranched portion by remote operation to bore the lining materialblocking a path to the branched pipe line (British Pat. No. 2,092,493).

In this device for boring, however, a means for exactly detecting theposition of an opening to a branched pipe line on the inner surface ofthe lined pipe line is quite necessary and a driving means for movingthe boring head is also necessary so that the device becomes inevitablycomplicated as a whole. Thus, such a device and method cannot be appliedto a pipe line having bends or to a pipe line of a small diameter.

A method disclosed in Japanese Laid-open Patent Appln. No. Sho. 55-41274is known, for example, as a method for boring a lining material atbranched portions of a pipe line after applying the lining material ontothe pipe line, without digging it up from the ground. This methodcomprises introducing an insert mass having a flexible conduit passingthrough the central core of the mass and extending backward into abranched portion of a pipe line the inner surface of which has beenbonded to the lining material, allowing pressure to act on the back ofthe insert mass while evacuating the air occupying the space in front ofthe insert mass through the flexible conduit thereby leading theflexible conduit to the opening for the branched pipe line, andthereafter sending a hot blast through the flexible conduit to thelining material bonded to the pipe line to bore it by fusion.

Another method is disclosed in Japanese Laid-open Patent Appln. No. Sho.58-49211 wherein an opening to a branch portion existing in a pipe lineis once clogged with a stopper prior to the application of a liningmaterial and the stopper is then allowed, after the application of thelining material, to become exothermic to use itself as a heating toolthereby boring the lining material bonded to the stopper by fusion.

According to the above known prior art wherein the insert mass or thestopper is allowed to advance and become located at the branched portionof the pipe line by fluid pressure, however, it is extremely difficultin the case of a small and multiple complicated bent branched pipe lineto lead the insert mass or the stopper to the branched portion by fluidpressure.

As the method disclosed in the above-mentioned Japanese Laid-open PatentAppln. No. Sho. 55-41274 wherein the boring operation has to beperformed by a hot blast, the boring operation is not easy. In addition,since a portion of the binder will flow into the branched pipe line andis solidified therein on bonding the lining material to the innersurface of the main pipe line, it is extremely difficult to fuse thelining material including such solidified binder for effecting theboring.

In the method disclosed in the above-mentioned Japanese Laid-open PatentAppln. No. Sho. 55-49211 wherein the stopper has to be initially mountedto the branched portion prior to the application of the lining material,it is not easy to mount the stopper correctly to the opening of thebranched portion. Further, this method has such a drawback that itcannot be applied to a pipe line to which a lining material has alreadybeen applied.

Under such circumstances, the present inventors have already invented aboring device which comprises a first flexible coil spring, a secondmore flexible compression coil spring connected to the front end of thefirst coil spring and an electric heater mounted to the tip of thesecond coil spring, operated in such a manner that the springs areintroduced into a pipe line while rotating the first coil spring so asto allow the electric heater to locate in the branched portion, andelectricity is sent to the heater to burn out the lining material. Thisapproach is applicable to a pipe line for which the lining treatment hasbeen finished, and is capable of being led to the branched portionthrough a branched pipe line having a small diameter and being curvedand bent, and easily capable of boring the lining material even in thecase of the branched pipe line having been filled with a large amount ofa binder flowed thereinto (Japanese Laid-open Utility Model Appln. No.Sho. 61-39400).

In this device wherein the boring device is introduced while rotatingthe first coil spring and rotationally shaking the front electric heaterby the resiliency of the second coil spring, however, the electricheater may thrust, at a joint such as LM joint in the pipe line, into aslit between the end of a straight pipe and the joint whereupon theweaker second coil spring buckles and is damaged to make it impossibleto move the heater forward beyond that point. Accordingly, the presentinventors further developed a boring device wherein the electric heateris surrounded with a thermoplastic resin to shape a block approximatelyin the form of a circular truncated cone mounted at the tip of thesecond coil spring (Japanese Utility Model Appln. No. Sho. 60-18915).

The device disclosed in the above mentioned Japanese Utility ModelAppln. No. Sho. 60-18915 wherein the electric heater is shaped to have aslanted side surface by coating with a thermoplastic resin can smoothlybe moved forward within the branched pipe line in compliance with thecurvature of the pipe line, avoiding a step formed at the LM joint orthe like and a barrier, such as flash. However, quite often the electricheater led to the branched portion did not function to send electricitythereto.

This situation caused by disconnection of the transmission wires is aphenomenon occurring in the coating of the resin or within the coilspring. It is apparent that this is ascribable to the transmission wiresbeing twisted off.

SUMMARY OF THE INVENTION

The present invention provides a boring device for a lining material forpipe lines, which overcomes the above mentioned problems. The presentinvention firstly provides a boring device for a lining material forpipe lines which comprises a tension coil spring, a compression coilspring connected to the tip of the tension coil spring and having aspring constant smaller than that of the tension coil spring, a headelement in the form of a circular truncated cone connected to the tip ofthe compression coil spring and comprised of an electric heat-generatingmeans coated with a thermoplastic resin and single or pluraltransmission wires connected to the electric heat-generating means beingpassed in a loosened state through the compression coil spring and thetension coil spring, the transmission wires being fixed within thetension coil spring at plural points, and a means provided at the rearof the tension coil spring for extending the spring in a rotationalmanner.

The present invention also provided a boring device of the abovementioned type, wherein an electric circuit is provided capable ofelectrically detecting a change in rotation speed of a rotor andtransmitting the change to the means for extending the spring so as tostop the rotation thereof and the extension of the tension coil spring.

The present invention further provides a boring device of the abovementioned type, wherein the electric circuit is provided with aproximity switch associated with the compression coil spring capable ofdetecting a change in impedance occurring in the switch on its use andtransmitting the change to the means for rotatably extending the tensioncoil spring so as to stop the rotation and extension of the tension coilspring.

The present invention still further provides a boring device of theabove mentioned type, wherein the head element is provided with athermocouple capable of detecting an electromotive force occurring inthe thermocouple on its use and transmit the force to the means forrotatably extending the tension coil spring so as to stop the rotationand extension of the tension coil spring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are respectively central longitudinal cross section viewsshowing an example of the boring device of the present invention.

FIG. 3 is a diagram showing the state of the boring device of thepresent invention being pushed forward while being rotated.

FIG. 4 is a diagram showing the state of a part of the coil spring ofthe boring device of the present invention being passed through a bendof a pipe line.

FIG. 5 is a diagram showing the state of the head element of the boringdevice of the present invention abutting against the lining material Ain the branched portion.

FIG. 6 is a diagram showing the state of the lining material A beingbored.

FIG. 7 is a diagram showing the state of the transmission wires in theboring device of the present invention being knitted.

FIG. 8 is a diagram showing an example of the electric circuit whereinthe head element is provided with a thermocouple or the compression coilspring with the proximity switch.

FIG. 9 is a diagram showing one example of the electric circuit in thecase of the boring device of the present invention provided with a meanspositioned in read of the tension coil spring for rotatably extendingthe device with a means for electrically detecting a change in rotationspeed of the rotor.

DETAILED DISCUSSION

The boring device of the present invention will now be explained in moredetail with reference to the accompanying drawings.

FIG. 1 shows one example of the boring device of the present invention.In FIG. 1, a tension coil spring 1 is provided in its rear end with ameans for rotatably extending the coil spring (not shown in FIG. 1 butdesignated simply as "N"). A commercially available drain cleaner or thelike can be used as the device N. As the tension coil spring is pushedforward and allowed to advance within a pipe line of a small diameter,however, the spring should preferably not be excessively flexible.

In FIG. 1, a compression coil spring 2 is connected through anothercompression coil spring 4 to the front end of the tension coil spring 1.The compression coil spring connected to the front end of the tensioncoil spring may be two compression coil springs connected in serieshaving different spring constants. In this case, the spring constant ofthe compression coil spring 4 connected to the tension coil springshould have a value between the spring constant of the compression coilspring 2 and the spring constant of the tension coil spring 1. In theboring device of the present invention, the compression coil spring 2alone can be used without another compression coil spring 4 so that thecompression coil spring 2 may be connected directly to the tension coilspring 1. This compression coil spring 2 is approximately identical indiameter with the head element 5 and is a sufficiently flexiblecompression coil spring having a spring constant smaller than that ofthe tension coil spring 1. The spring constant of the compression coilspring 4 is within the range between the tension coil spring 11 and thecompression coil spring 2 with respect to spring constant so that thecompression coil spring 4 has a flexibility ranking between the tensioncoil spring 1 and the compression coil spring 2.

The head element 5 is provided in the central part thereof with anelectric heat-generating means 3 (for example, an electrical heater) andis mounted to the tip of the compression coil spring 2. Theheat-generating means 3 is covered with a thermoplastic resin 6 to forma block as a whole. The head element 5 has an outer diameter slightlysmaller than the minimum diameter of a pipe line into which the boringdevice of the present invention is to be inserted.

Used as the heat-generating means 3 is, for example, a Ni-Cr hot plateor a relatively thick Ni-Cr wire 7 in a vortex form. Used as thethermoplastic resin 6 are elastic thermoplastic resins such aspolyurethane resins, soft vinyl chloride resins and EVA resins. Theelectric heat-generating means 3 is covered with the resin and shapedinto a block in the form of a circular truncated cone to form the headelement 5.

The outer end of the hot panel or hot wire 7 of the heat-generatingmeans 3 is connected to the tension coil spring 1 through thecompression coil springs 2 and 4 while the inner end of the hot panel orhot wire 7 is connected to a transmission wire 9 through a screw 8. Thetransmission wire 9 extends backward in a sufficiently loosened statethrough the compression coil springs 2 and 4 and the tension coilspring 1. This state can be achieved by passing the transmission wire 9through the coil springs in a stretched state, rewinding the coilsprings circularly and again drawing out the coil springs to theoriginal position. The transmission wire 9 is passed through thecompression coil springs in a loosened state but is fixed in a suitablemanner at a proper interval to the tension coil spring 1. In thisexample, the transmission wire 9 is passed through the coil spring in astretched state on a platform and then the coil spring is wound upcircularly whereby the valleys of the spring are opened. A thermoplasticresin 10, such as EVA resin, is injected into the valleys and thencooled whereby the transmission wire 9 is easily fixed to the tensioncoil spring 1. Any thermoplastic resin such as that used to form thehead element 5 can be used.

Referring to FIGS. 2A and 2B, another example is explained whereinplural transmission wires 9 are passed through the coil springs.Thermocouple 11 is a heat-sensing means. The head element 5, shaped withthe thermoplastic resin 6 into a block, is provided on the top with thethermocouple 11 having a first lead wire 12 extending therefromconnected to the tension coil spring 1 through the compression coilsprings 2 and 4 and a second lead wire 13 extending backwards throughthe interior space of the compression coil springs 2 and 4 and thetension coil spring 1.

On boring the lining material of the pipe line with the boring device ofthe present invention, the thermocouple 11 functions as follows. Afterpressing the lining material onto the inner surface of the pipe line bythe aid of a binder, a warming pressurized fluid is allowed to enter andflow through the interior space of the pipe line to warm the liningmaterial while pressing it against the inner surface of the pipe line tocure the binder. Illustrative of the warming pressurized fluid are warmwater, hot blast (air), steam and a mixture of steam and hot blast.These fluids may be introduced into the tubular lining material from oneend thereof. However, it is one of the preferred methods to introduce ahose having a great number of small pores into the interior space of thelining material and to pass the above mentioned fluid through the hosewhereby the fluid is leaked out of the hose through the small pores orpinholes for warming.

The boring device of the present invention is inserted into the pipeline from one end of the branched pipe line and positioned at thebranched portion while bonding the binder in such manner. The front endof the boring device, i.e. the head element 5, is introduced into thebranched pipe line from the terminal end thereof and the tension coilspring 1 is allowed to proceed within the branched pipe line whilerotating the coil spring.

When the front end of the boring device, i.e. the head element 5,reaches the branching portions of the branched pipe line, the headelement 5 is maneuvered to abut against the outer surface of the liningmaterial blocking the passage to the branch of the pipe line (FIG. 5).As the lining material is warmed by the warming pressurized fluid, theheat is detected by the thermocouple 11 mounted at the top of the headelement 5 whereby the difference in voltage created between the leadwires 12 and 13 (electromotive force) is detected by a temperaturedetector. The detected difference in voltage is transmitted to a meansfor rotatably extending the tension coil spring. An electric circuit isprovided so as to stop the rotation and extending of the tension coilspring by transmission of the difference in voltage. One example of suchan electric circuit is shown in FIG. 8. Referring to FIG. 8, thedifference in voltage is detected by a temperature detector 31 whereby aswitch 32 normally implemented for turning on a motor 36, is turned offto stop the operation of the motor 36, while turning on a switch 33normally implemented for turning off an electromagnetic brake 39, toactuate the electromagnetic brake 39 for stopping a shaft 37 therebystopping the rotating and extension of the means for rotatably extendingout the tension coil spring 1 driven by a belt 38. As a result, the headelement 5 of the boring device is kept in contact with the liningmaterial at the branched portion.

A proximity switch 14 is present for detecting the arrival of theelectric heater 3 At the branched portion. This proximity switch 14 isinstalled between the compression coil spring 2 and the compression coilspring 4 in such a manner that a cylinder 15 made of a synthetic resinhas a groove 16 on its outer surface and a coil 17 of an enamel wire isprovided in the groove 16. The coil 17 is overlaid with a protectivetube 18 and a lead wire 19 from the coil 17 extends backwards throughthe compression coil spring 4 and the tension coil spring 1.

In this example, the transmission wires 9 from the head element and thelead wires 13 and 19 from the thermocouple 11 are the proximity switch14, respectively, are previously kept in loosely knitted state 23 (FIG.7) and passed through the tension coil spring in a well loosened state24. As in the case of the previous example, the transmission wires 9 orthe lead wires 13 and 19 are fixed to the tension coil spring 1.

On boring the lining material of the pipe line with the boring device ofthe instant invention, the proximity switch 14 functions as follows. Theboring device provided with the proximity switch 14 is used, prior toapplying a lining to the main pipe line, in such a manner that theboring device is inserted from one end of the branched pipe line towardthe branched portions and the front end of the boring device, i.e. thehead element 5, is located at a given position of the branched portionprior to the lining treatment of the main pipe line. Prior to the liningtreatment, the boring device of the invention is inserted from the endof the branched pipe line and allowed to advance toward the branchedportion. In this case, the proximity switch 14 is allowed to advancewhile keeping the device close to the inner surface of the branched pipeline. When a high frequency current is sent to the coil 17 from anamplifier 31 (FIG. 8) having a high frequency emission circuit, anychange is detected by the impedance produced therein.

When the front end of the boring device of the invention reaches thebranching portion and is allowed to advance further and enter in themain pipe line, the portion of the device provided with the proximityswitch 14 also enters in the main pipe line whereupon the wall surfaceof the branched pipe line around the periphery of the proximity switchno longer exists and thus a change occurs in impedance of the coil 17.An electric circuit is installed so as to stop the rotation andextension of the tension coil spring by this change in impedance. Suchelectric circuit can be explained by utilizing FIG. 8. Referring to FIG.8, the change in impedance is detected in the amplifier 31 to turn offthe normally turned-on switch 32 for the motor 36 to stop the sending ofelectricity thereto and on the other hand to turn on the normallyturned-off switch 33 for the electromagnetic brake 39 for sendingelectricity thereto whereupon the rotation of the shaft 37 is stopped asis the rotatable extension of the tension coil spring 1. As a result,the advance of the boring device is stopped just after the portionprovided with the proximity switch 5 is allowed to enter the main pipeline.

Next, the rotation of the device N for rotatably extending the spring isreversed to pull back the tension coil spring 1 by a distancecorresponding to the length from the proximity switch 14 to the headelement 5 whereby the head element 5, provied with the electric heater3, can be located exactly in a given pipe of the branched portion.

The main pipe line is then lined with a lining material under pressure.The opening to the branched pipe line is blocked with the liningmaterial applied to the main pipe line by this lining treatment. Thisstate is shown in FIG. 5.

In each of the above examples, the individual coil springs can freely beconnected or disconnected by way of a connector 22, including connectionor disconnection of transmission wires passing through the individualcoil springs. In this case, the shape and mechanism of the connector, aswell as connection and joint of the electric system, can properly beselected.

In order to introduce the boring device of the present invention intothe branched pipe line, the front end of the device provided with thehead element 5 is inserted into the branched pipe line from the terminalend thereof and moved forward while rotating the tension coil spring.

When the tension coil spring 1 is rotated, the compression coil spring 2is also rotated through the other compression coil spring 4 androtationally shaken while shaking the head element as shown in FIG. 3,since the compression coil spring 2 is more flexible than the tensioncoil spring. At a bend portion of the pipe line, the head element 5 ismoved forward smoothly along the bend while detecting the direction ofthe bend. As the head element 5, including the electric heater 3 coveredwith a thermoplastic resin 6, is shaped to have a slanted side surface,the head element 5 is moved forward smoothly within the pipe line,avoiding the end of the straight pipe or end stopper at LM joints andthe like.

The rotation force is also applied to the transmission wires passingthrough the coil springs. As the transmission wires are fixed within thetension coil spring at a proper distance to the spring, the rotationforce is transmitted to the front end of the transmission wires in thelengthwise direction thereof.

As the transmission wires are passed through the coil springs in aloosened state, there is no fear of disconnection even if the coilsprings are somewhat elongated whenever the coil springs pass through abend, so that the transmission wires are allowed to pass, together withthe coil springs, through the branched pipe line without any damage(FIG. 4).

When the head element 5 reaches the branched portion 25 of the branchedpipe line (FIG. 5), the rotation and extending of the tension coilspring 1 are stopped and the head element 5 is allowed to abut againstthe lining material A blocking the path to the branch portion of thepipe line at the branched portion by the resiliency of the compressioncoil spring 2, as shown in FIG. 5. A switch for the head element isturned on in this state to send electricity to a hot plate or wire 7 toactuate the electric heater 3 whereby the thermoplastic resin 6 coveringit is made molten and the lining material A is then made molten andbored by the self-weight of the head element 5, the resiliency of thecompression coil spring 2 and the heat generated by the electric heater3 (FIG. 6), switch 35 and the electric source 34 (FIGS. 8 and 9).

In an embodiment of the boring device of the invention, an electriccircuit can be installed which is capable of electrically detecting achange in rotation speed of a rotor in the means for rotatably extendingthe tension coil spring and transmitting the change to the means forrotatably extending the tension coil spring to stop the rotation andextending of the tension coil spring. An example of such an electriccircuit is shown in FIG. 9. Referring to FIG. 9, the circuit showntherein is provided with the means N for rotatably extending the tensioncoil spring 1 having a rotor R equipped with a reflection tape 40 on apart of its peripheral surface and is also provided with a photoelectricswitch 41 as a non-contact output-type switch located in a position nearto the locus of the rotor R. The photoelectric switch 41 is connected toa motion detector 42 which records the signal from the switch 41 as apulse and measures the time interval between pulses. If the timeinterval exceeds a given length, a normally turned-on switch 32 for amotor 36 is turned off, and on the other hand, a normally turned-offswitch 33 of a circuit for an electromagnetic brake 39 is turned on.

Regarding the use of the boring device of the present invention providedwith the means for electrically detecting a change in rotational speedof the rotor and transmitting the change to the means for extending thetension coil spring, the boring device functions as follows.

When the boring device of the invention is inserted into the branchedpipe line and pushed forward and when the front end of the device ispushed against a step within the pipe line or a lining material A havingbeen applied to the pipe line in the branched portion (FIG. 5), therotation of the head element 5 becomes significantly slowed and isstopped. The rotation of the tension coil spring continues even in sucha case so that the compression coil spring 2 is severely twisted.Accordingly, the rotation of the tension coil spring 1 is decelerated bythe resistance of the compression coil spring 2 to increase the load onthe rotor R thereby decelerating its rotation. As a result, thefrequency of detecting the reflection tape 40 becomes smaller in thephotoelectric switch 41 so that the interval between pulses in themotion detector 42 becomes greater. When the interval becomes largerthan a given length, the motion detector 42 emits a signal whereby thenormally turned-on switch 32 for the motor circuit is turned off to stopthe sending of electricity to the motor 36 and, on the other hand, thenormally turned-off switch 33 is turned on to actuate theelectromagnetic brake 39 for stopping the rotation of the rotating shaft37.

The rotation of the rotor R is thus immediately allowed to stop and therotation and extending of the tension coil spring 1 is concurrentlystopped to prevent any further twisting of the compression coil spring2.

A combination of the above detecting means with the non-contact,output-type switch is not limited to a combination of the reflectiontape 40 with the photoelectric switch 41. Whatever means can be appliedthat is suitable as far as it can detect a change in rotation speed andtransmit it electrically.

In the boring device of the present invention, the transmission wires 9and the like can be inserted in a knitted state 23 (FIGS. 2 and 7) intothe coil springs whereby a uniformly loosened state can be imparted tothe transmission wires 9 and the like. Thus, the transmission wires 9and the like are not subjected discretely to elongation. Even if theyare twisted, they are easily reinstated to their original state.

The boring device of the present invention provided at the front endthereof with a head element in the form of a circular truncated coneinvolving an electric heat-generating means covered with a thermoplasticresin can be inserted into branched pipe lines and moves forwardsmoothly therein even if steps and obstacles exist in the branched pipelines.

In the boring device of the invention, the transmission wires are passedin a loosened state through the compression coil spring and the tensioncoil spring and fixed at plural points to the tension coil spring. Thus,there is no fear of disconnection of the transmission wires when theboring device is pushed forward within the pipe line while beingrotated.

As the boring device of this invention has the head element provided atthe tip thereof with a thermocouple or has the compression coil springprovided with aa proximity switch, the front end of the boring devicecan be allowed to arrive exactly at a lining material in the branchedportion of the branched pipe line which is to be bored.

In the boring device of this invention, the means for rotatablyextending the tension coil spring can be provided with a means forelectrically detecting a change of rotation speed of the rotor whichenables advancing and stopping of the boring device within the pipe linefreely.

The boring device of this invention does not necessitate the use of anyfluid pressure. Thus, no back pressure is applied to the device and thetransmission wires can be passed very easily through the branched pipeline having a number of bends without being twisted.

Even if the pipe line is bent upward, the transmission wires can bepassed therethrough in compliance with the bent direction. Further, thedevice can easily and smoothly be inserted into the branched pipe line,avoiding steps and obstacles therein.

The use of loosely knitted transmission wires can easily present thewires in a uniformly loosened state in the coil springs and make itpossible to untwist the wires so that the force applied to thetransmission wire can be absorbed by the whole of the transmission wiresin loosely knitted form.

On boring of the lining material, the electric heater may be stainedwith the burned ashes and residue of the lining material and binderthereby seriously lower the boring ability of the heater on its reuse.The individual compression coil springs can thus be connected by way ofconnectors to make it convenient to exchange the used electric heaterwith a new one. Each part can be manufactured as a cartridge type partto facilitate exchange of one part with a new one. It is also convenientto use transmission wires in the compression coil spring which are finerthan those in the tension coil spring so that good flexibility of thecompression coil spring may not be effected.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the present invention, and allsuch modifications as would be obvious to one skilled in the art areintended to be included within the scope of the following claims.

We claim:
 1. A boring device for a lining material for pipe lines whichcomprises in combination a tension coil spring, a compression coilspring being connected to a tip of said tension coil spring and having aspring constant smaller than that of said tension coil spring, a headelement in the form of a circular truncated cone being connected to atip of the compression coil spring and comprising an electricheat-generating means coated with a thermoplastic resin, a single orplural transmission wires being connected to said electricheat-generating means, passed in a loosened state through said tensioncoil spring and said compression coil spring, said transmission wiresbeing fixed within said tension coil spring at plural points, and ameans provided in a rear of said tension coil spring for rotatablyextending said boring device.
 2. A boring device for lining materialsfor pipe lines according to claim 1, wherein said device is providedwith an electric circuit in such a manner that the head element isprovided at a top thereof with a thermocouple capable of detectingelectromotive force occurring in said thermocouple on its use andtransmitting said force to the means for rotatably extending saidtension coil spring so as to stop the rotation and extension of saidtension coil spring.
 3. A boring device for lining materials for pipelines according to claim 1, wherein said device is provided with anelectric circuit in such a manner that said compression coil spring isprovided with a proximity switch capable of detecting a change inimpedance occurring in said switch on its use and transmitting thechange to the means for rotatably extending said tension coil spring soas to stop the rotation and extending of said tension coil spring.
 4. Aboring device for lining materials for pipe lines according to claim 1,wherein said device is provided in said means for rotatably extendingsaid tension coil spring with an electric circuit capable ofelectrically detecting a change in rotation speed of a rotor andtransmitting the change to said extension means so as to stop therotation and extension of said tension coil spring.
 5. A boring devicefor lining materials for pipe lines according to claim 1, wherein saidplural transmission wires in a loosened state are made by looselyknitting the wires.
 6. A boring device for lining materials for pipelines according to claim 1, wherein said transmission wires are fixed tothe tension coil spring by the aid of a thermoplastic resin.
 7. A boringdevice for lining materials for pipe lines according to claim 1, whereinsaid compression coil spring consists of two compression coil springsconnected in series having different spring constants, the compressioncoil spring connected to the tension coil spring having a springconstant of a value between the spring constant of the tension coilspring and that of the other compression coil spring.
 8. A boring devicefor lining materials for pipe lines according to claim 1, whereinconnection or disconnection of the individual springs including thetransmission wires being passed therethrough is freely effected by wayof a connector.
 9. A boring device for lining materials for pipe linesaccording to claim 1, wherein the head element is connected in the formof a cartridge type connector to said compression coil spring.
 10. Aboring device for lining materials for pipe lines according to claim 1,wherein each part, from the head element to the connector of eachspring, is in the form of a cartridge.